linux-kernel - Re: [PATCH v7 9/9] docs: ABI: testing: Document the Ampere Altra Family's SMpro sysfs interfaces

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Date:   Mon, 21 Mar 2022 16:46:36 +0700
From:   Quan Nguyen <quan@...amperecomputing.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Lee Jones <lee.jones@...aro.org>, Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Jean Delvare <jdelvare@...e.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Jonathan Corbet <corbet@....net>,
        Derek Kiernan <derek.kiernan@...inx.com>,
        Dragan Cvetic <dragan.cvetic@...inx.com>,
        Arnd Bergmann <arnd@...db.de>,
        Thu Nguyen <thu@...amperecomputing.com>,
        Gustavo Pimentel <Gustavo.Pimentel@...opsys.com>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        "open list:HARDWARE MONITORING" <linux-hwmon@...r.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        OpenBMC Maillist <openbmc@...ts.ozlabs.org>,
        Open Source Submission <patches@...erecomputing.com>,
        Phong Vo <phong@...amperecomputing.com>,
        "Thang Q . Nguyen" <thang@...amperecomputing.com>
Subject: Re: [PATCH v7 9/9] docs: ABI: testing: Document the Ampere Altra
 Family's SMpro sysfs interfaces



On 21/03/2022 15:23, Greg Kroah-Hartman wrote:
> On Mon, Mar 21, 2022 at 03:13:55PM +0700, Quan Nguyen wrote:
>> Add documentation for the Ampere(R)'s Altra(R) SMpro sysfs interfaces
>>
>> Signed-off-by: Quan Nguyen <quan@...amperecomputing.com>
>> ---
>> Changes in v7:
>>    + First introduce in v7     [Greg]
>>
>>   .../sysfs-bus-platform-devices-ampere-smpro   | 133 ++++++++++++++++++
>>   1 file changed, 133 insertions(+)
>>   create mode 100644 Documentation/ABI/testing/sysfs-bus-platform-devices-ampere-smpro
>>
>> diff --git a/Documentation/ABI/testing/sysfs-bus-platform-devices-ampere-smpro b/Documentation/ABI/testing/sysfs-bus-platform-devices-ampere-smpro
>> new file mode 100644
>> index 000000000000..9bfd8d6d0f71
>> --- /dev/null
>> +++ b/Documentation/ABI/testing/sysfs-bus-platform-devices-ampere-smpro
>> @@ -0,0 +1,133 @@
>> +What:		/sys/bus/platform/devices/smpro-errmon.*/errors_[core|mem|pcie|other]_[ce|ue]
> 
> Please split this out as one entry per file.
> 

These sysfs share same format of HW errors (the 48-byte Arm vendor 
specific HW error record) but for separate HW domains: Core, PCIe, 
Mem... etc

>> +KernelVersion:	5.14
> 
> 5.14 is a long time ago.
> 
>> +Contact:	quan@...amperecomputing.com
>> +Description:
>> +		(RO) Contains the 48-byte Ampere (Vendor-Specific) Error Record, see [1]
>> +		printed in hex format as below:
>> +
>> +		AA BB CCCC DDDDDDDD DDDDDDDDDDDDDDDD DDDDDDDDDDDDDDDD \
>> +		   DDDDDDDDDDDDDDDD DDDDDDDDDDDDDDDD DDDDDDDDDDDDDDDD
>> +		Where:
>> +		  AA       : Error Type
>> +		  BB       : Subtype
>> +		  CCCC     : Instance
>> +		  DDD...DDD: Similar to the Arm RAS standard error record
> 
> No, this is not a valid sysfs file, sorry.  This should just be one
> value per file.
> 

This 48-byte value is unable to separate into smaller values because it 
contain all information necessary to indicate a single HW error as per 
ARM RAS supplement document [1]. The format is to make it read-able 
other than a single 48-byte hex value.

[1] https://developer.arm.com/documentation/ddi0587/latest/

> 
>> +
>> +		See [1] below for the format details.
>> +
>> +		The detail of each sysfs entries is as below:
>> +		+-------------+---------------------------------------------------------+
>> +		|   Error     |                   Sysfs entry                           |
>> +		+-------------+---------------------------------------------------------+
>> +		| Core's CE   | /sys/bus/platform/devices/smpro-errmon.*/errors_core_ce |
>> +		| Core's UE   | /sys/bus/platform/devices/smpro-errmon.*/errors_core_ue |
>> +		| Memory's CE | /sys/bus/platform/devices/smpro-errmon.*/errors_mem_ce  |
>> +		| Memory's UE | /sys/bus/platform/devices/smpro-errmon.*/errors_mem_ue  |
>> +		| PCIe's CE   | /sys/bus/platform/devices/smpro-errmon.*/errors_pcie_ce |
>> +		| PCIe's UE   | /sys/bus/platform/devices/smpro-errmon.*/errors_pcie_ue |
>> +		| Other's CE  | /sys/bus/platform/devices/smpro-errmon.*/errors_other_ce|
>> +		| Other's UE  | /sys/bus/platform/devices/smpro-errmon.*/errors_other_ue|
>> +		+-------------+---------------------------------------------------------+
>> +		UE: Uncorrect-able Error
>> +		CE: Correct-able Error
>> +
>> +		[1] Section 3.3 Ampere (Vendor-Specific) Error Record Formats,
>> +		    Altra Family RAS Supplement.
>> +
>> +
>> +What:           /sys/bus/platform/devices/smpro-errmon.*/errors_[smpro|pmpro]
>> +KernelVersion:	5.14
>> +Contact:	quan@...amperecomputing.com
>> +Description:
>> +		(RO) Contains the internal firmware error record printed as hex format
>> +		as below:
>> +
>> +		A BB C DD EEEE FFFFFFFF
> 
> Again this isn't a good sysfs entry.  You should never have to parse a
> sysfs file except for a single value.
> 
> thanks,
> 
> greg k-h

This error is also unable to separate further as well.

Thanks Greg for the review.
- Quan